Rare and valuable minerals

How to distinguish a synthetic diamond from a real one?

An artificial diamond is a stone almost identical in composition to a natural diamond, grown under special laboratory conditions. Do not confuse artificial diamonds with cubic zirconia and moissanite. If with the last two a natural diamond has many differences that make it possible to identify a fake using even home tests, then in the case of an artificial diamond everything is much more complicated. Let’s try to figure it out.

Artificial diamonds – what are they and how are they made?

The first artificial diamonds were synthesized back in the 50s of the 90th century. But it was only in the XNUMXs that samples were brought to sizes that would be of interest to the jewelry industry. Today there are two main production technologies.

Synthesis of HPHT

The technology of growing diamonds in small capsules under high pressure (from high-pressure high-temperature – “high pressure and temperature”). The raw material is diamond powder, which is dissolved in molten metal flux and then crystallized on a seed. The growing process takes from a couple of weeks to several months. Most HPHT diamonds are yellow, orange-yellow, or brown-yellow in color. By adding inhibitors, transparent and blue stones are obtained, and by adding boron, blue stones are obtained.

CVD synthesis

The technology of growing diamonds using a laser inside a vacuum chamber filled with carbon-containing gas (from chemical vapor deposition). The laser destroys gas molecules, causing carbon atoms to settle on the seed plates. The growth rate is several weeks. CVD technology allows you to grow several samples simultaneously. Most CVD diamonds are brown or gray in color. When nitrogen or boron is added to the chamber, yellow, pink-orange or blue stones are obtained. To obtain clear samples, CVD brown diamonds are decolorized using HPHT technology.

How to distinguish a natural diamond from a synthetic one

Unfortunately, for ordinary people, determining the naturalness of a stone is only possible with the help of special gemological equipment and tests.

Color zoning

  • Colored diamonds grown using HPHT technology have color zoning according to a geometrically ideal pattern.
  • Natural diamonds may also exhibit color zoning, but it will not follow any geometric pattern.
  • CVD diamonds have a perfectly even color distribution throughout the entire sample.

Thus, using a microscope, a gemologist can understand which stone is in front of him based on the type of color zoning.

Metal and graphite inclusions

Due to the peculiarities of the technology, HPHT diamonds often have inclusions of hardened metal, while CVD diamonds often contain graphite. They can only be seen with very high magnification. But HPHT stones react to a strong magnet: up to 95% of samples of such synthetic diamonds have magnetic properties. Thus, the magnet test allows only HPHT diamonds to be “rejected”. A detailed examination of samples under powerful magnifying technology will reveal inclusions of metal and graphite, which will most likely indicate the synthetic nature of the stone.

Note that natural diamonds can also contain inclusions of graphite, ilmenite, magnetite, garnet, malacolite, etc. But, as a rule, these inclusions have a typical “feather” appearance – an experienced gemologist can immediately determine their natural origin.

Interference (deformation) of colors

This test is based on placing the diamond between two polarizing filters at an angle of 90 degrees to each other. Natural stone will exhibit a cross-hatching or mosaic pattern of color interference that occurs due to uneven pressure being applied to the crystal during the growth period. Synthetic stones grown at constant pressure values ​​do not show a color deformation pattern.

Fluorescence

The fluorescence of synthetic diamonds has a characteristic pattern. For HPHT stones it has a cross-shaped shape, and for CVD stones it has a striped pattern. Under a UV lamp, HPHT synthetics often have a green, yellow-green or yellow color, while CVD synthetics are predominantly orange or red. But natural diamonds glow blue.

Figure 1. On the left is a CVD diamond, in the center is an HPHT diamond, on the right is a natural diamond.

A special DiamondView installation allows fluorescence visualization to reveal patterns of crystal growth. Based on the picture, it becomes clear which sample is in front of the gemologist – HPHT, CVD or natural stone. Unfortunately, the cost of installation is so high that they are not found in domestic laboratories.

Figure 2. Cross-shaped patterns of HPHT diamonds when viewed on DiamondView.

Phosphorescence

After turning off the UV lamp, natural stones “go out”, but synthetics (especially HPHT) can glow for more than a minute.

To summarize, we can say that to accurately determine the origin of a diamond, special expensive equipment is needed: refractometers, ultraviolet gemological lamps, polariscopes and microscopes. They cannot be found in all laboratories. Therefore, in order not to guess what kind of stone you purchased, it is better to make purchases exclusively in trusted places.

All diamonds in our showroom are completely natural. They are certified by the independent gemological center of Moscow State University. The stones are accompanied by a certificate indicating the main characteristics of natural stone, as well as a number and a link to the test laboratory report.

According to De Beers Corporation, which mines, processes and sells natural diamonds, every second diamond in the world is fake. How to understand that they are trying to deceive you?

How a fraudster invented jewelry

Few people know, but jewelry began with deception. The accessories that are now in the arsenal of almost every lady have been in common use for quite some time and are the result of the ingenuity of an enterprising adventurer.

His name was Georges Frederic Strass. He was a jeweler and in the 19th century he invented the technology for producing potassium glass, in which the concentration of lead exceeded the usual values. By giving this material a special cut, Strass created the perfect fake, which was difficult to distinguish from a real diamond for a layman. Luxury lovers bought the purest shining gems, not suspecting that they were paying a lot of money for an ordinary piece of glass.

After Strass’s death, such stones began to be called rhinestones in his honor. And later, the Czech engineer Daniel Swarovski invented a unique machine for grinding rock crystal and founded the Swarovski company. Until now, the company’s crystal cutting technology remains secret.

Diamond Quality Standards

Cut. The most popular and most expensive round diamonds are Kr-57 cut. These diamonds have the most brilliant play of all cut shapes. Fancy cut shapes – marquise, princess, heart, pear and others – have a special unique appeal and look great in jewelry.

Weight. The weight of diamonds is measured to the nearest 0,01 carats. One carat is equal to 200 milligrams. The weight of diamonds is measured on special carat scales, and it can be approximately determined by the diameter of the stone

Color. Diamonds vary in color from colorless to yellow. To correctly determine the color, a diamond is compared with standards and assigned an appropriate index on the color scale. Other colors – fancy (yellow, orange, pink, blue, green and others) are quite rare.

Purity. Diamonds, like most other minerals, are characterized by natural inclusions and defects. In order to determine the clarity of a diamond, it is necessary to determine the number and nature of defects, as well as their size and location.

It is worth noting that there is no single standard for the parameters of the color and clarity of a diamond and they may differ from each laboratory or seller, but the GIA standard is generally accepted in the world, and in Russia – TU 117-4.2099-2002.

Identifying a diamond by eye: is it possible?

Hardly ever. Today, even a specialist, simply by looking at a stone, will not be able to absolutely accurately determine its authenticity. Purity, luminescence, thermal and electrical conductivity do not provide even 90% confidence. Often, even the latest generation portable testers (Presidium Multitester III) mistake high-quality moissanite for a diamond.

Synthetic moissanite is the highest quality diamond imitation available today. At the same time, technologies for the artificial cultivation of diamonds, which in their chemical composition are indistinguishable from natural ones, are now rapidly developing. Only large gemological laboratories can distinguish an artificially grown diamond from a natural one.

So how do you know if a stone is natural?

The tag of a diamond product may not contain any indication of artificial origin, and the only guarantee for the buyer is a certificate from a large laboratory with a good reputation.

The most respected certification centers are GIA (Gemological Institute of America), AGS (American Gemological Society), IGI (International Gemological Institute), HRD (Higher Diamond Council).

A certificate is a kind of diamond passport, which indicates its individual characteristics.

Don’t be shy and always ask the seller for a certificate for the stone. The specialist will not be offended by such a request and will provide you with all the documents without further ado. But the scammer has nothing to show you, and you can draw certain conclusions based on the person’s reaction alone.

Very often you can find advertisements for the sale of diamonds below exchange prices, for example -20%, -40% from Rapaport, etc. In this case, as a rule, they are trying to deceive you about the origin of the stone (selling synthetic instead of natural) or about the characteristics of the stone (color, purity). To protect yourself, you need to take a certificate for the stone from the seller and do several checks:

  • Check the certificate for authenticity on the website of the laboratory that issued the certificate and check all the parameters of the stone;
  • Check for laser engraving with the certificate number on the girdle of the stone (you can clearly see the engraving with a 20x magnifying glass);
  • Check the actual dimensions of the stone with the dimensions indicated in the certificate; there should be no deviation in any dimension by more than 0,05 mm (for this you will need a high-quality micrometer).

The described actions will protect you from fraud by 95%. When purchasing a particularly valuable diamond, it is advisable to invite an independent gemologist to handle the transaction.

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